<PAGE>

CONFIDENTIAL TREATMENT REQUESTED. CONFIDENTIAL PORTIONS OF THIS DOCUMENT HAVE
BEEN REDACTED AND HAVE BEEN SEPARATELY FILED WITH THE COMMISSION.

                                                                   EXHIBIT 10.40

     THIS WARRANT AND THE COMMON STOCK ISSUABLE UPON THE EXERCISE HEREOF HAVE
     NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933. THEY MAY NOT BE SOLD,
     OFFERED FOR SALE, PLEDGED, HYPOTHECATED, OR OTHERWISE TRANSFERRED EXCEPT
     PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF
     1933, OR AN OPINION OF COUNSEL SATISFACTORY TO THE COMPANY THAT
     REGISTRATION IS NOT REQUIRED UNDER SUCH ACT OR UNLESS SOLD PURSUANT TO RULE
     144 UNDER SUCH ACT.

WARRANT TO PURCHASE 500,000             ISSUE DATE:      AUGUST 7, 2000
SHARES OF THE COMMON                    EXPIRATION DATE: AUGUST 7, 2005
STOCK OF CONDUCTUS, INC.                INITIAL EXERCISE PRICE: $13.43 PER SHARE


            This Warrant is issued to Dobson Communications Corporation or its
registered assigns ("Holder") by Conductus, Inc., a Delaware corporation (the
"Company"), on August 7, 2000 (the "Warrant Issue Date"). This Warrant is issued
pursuant to the terms of that certain Purchase Agreement between Conductus, Inc.
and Dobson Cellular Systems, Inc. (the "Purchase Agreement") dated August 7,
2000.

            1.  PURCHASE SHARES. Subject to the terms and conditions hereinafter
set forth, the Holder is entitled, upon surrender of this Warrant at the
principal office of the Company (or at such other place as the Company shall
notify the Holder in writing), to purchase from the Company up to five hundred
thousand (500,000) fully paid and nonassessable shares of Common Stock of the
Company, as constituted on the Warrant Issue Date (the "Common Stock"). The
number of shares of Common Stock issuable pursuant to this Section 1 (the
"Shares") shall be subject to adjustment pursuant to Section 7 hereof.

            2.  EXERCISE PRICE. The purchase price for the Shares shall be
$13.43, as adjusted from time to time pursuant to Section 7 hereof (the
"Exercise Price").

            3.  EXERCISE PERIOD. This Warrant shall be exercisable as follows:

                a. Warrants shall become exercisable fifteen (15) days after the
close of each of the Company's business quarters (October 15, 2000 through
October 15, 2002) as to the number of shares determined by dividing the total
revenue to the Company from purchases by Dobson Cellular Systems, Inc. under the
Purchase Agreement during the quarter by [***];

                b. Warrants shall remain exercisable until 5:00p.m. on August 7,
2005;


------------------------
[***] Confidential material redacted and filed separately with the Commission.

<PAGE>

provided, however, that in the event of (a) the closing of the Company's sale or
transfer of all or substantially all of its assets, or (b) the closing of the
acquisition of the Company by another entity by means of merger, consolidation
or other transaction or series of related transactions, resulting in the
exchange of the outstanding shares of the Company's capital stock such that at
least 50% of the voting power of the Company is transferred, this Warrant shall,
on the date of such event, no longer be exercisable and become null and void. In
the event of a proposed transaction of the kind described above, (i) the Company
shall notify Holder as soon as practicable, but no less than twenty (20)
business days before the consummation of such event or transaction, and (ii)
accelerate vesting of warrants as to those shares earned in accordance with
paragraph 3(a) that are earned between the end of the last completed quarter and
the date of the transaction.

            4.  METHOD OF EXERCISE. While this Warrant remains outstanding and
exercisable in accordance with Section 3 above, the Holder may exercise, in
whole or in part, the purchase rights evidenced hereby. Such exercise shall be
effected by:

                (a) the surrender of the Warrant, together with a duly executed
copy of the form of Notice of Election attached thereto, to the Secretary of the
Company at its principal offices; and

                (b) the payment to the Company of an amount equal to the
aggregate Exercise Price for the number of Shares being purchased.

            5.  CERTIFICATES FOR SHARES. Upon the exercise of the purchase
rights evidenced by this Warrant, one or more certificates for the number of
Shares so purchased shall be issued as soon as practicable thereafter (with
appropriate restrictive legends, if applicable).

            6.  ISSUANCE OF SHARES. The Company covenants that the Shares, when
issued pursuant to the exercise of this Warrant, will be duly and validly
issued, fully paid and nonassessable and free from all taxes, liens, and charges
with respect to the issuance thereof.

            7.  ADJUSTMENTS OF EXERCISE PRICE AND NUMBER OF SHARES. The number
of and kind of securities purchasable upon exercise of this Warrant and the
Exercise Price shall be subject to adjustment from time to time as follows:

                (a) SUBDIVISIONS, COMBINATIONS OR OTHER ISSUANCES. If the
Company shall at any time prior to the expiration of this Warrant subdivide its
Common Stock, by split-up or otherwise, or combine its Common Stock, or issue
additional shares of its Common Stock as a dividend with respect to any shares
of its Common Stock, the number of Shares issuable on the exercise of this
Warrant shall forthwith be proportionately increased in the case of a
subdivision or stock dividend, or proportionately decreased in the case of a
combination. Appropriate adjustments shall also be made to the purchase price
payable per share, but the aggregate purchase price payable for the total number
of Shares purchasable under this Warrant (as adjusted) shall remain the same.
Any adjustment under this Section 7(a) shall become effective at the close of
business on the date the subdivision or combination becomes effective, or as of
the record date of such dividend, or in the event that no record date is fixed,
upon the making of such dividend.

                                       2

<PAGE>

                (b) RECLASSIFICATION, REORGANIZATION AND CONSOLIDATION. In case
of any reclassification, capital reorganization, or change in the Common Stock
of the Company (other than as a result of a subdivision, combination, or stock
dividend provided for in Section 7(a) above), then, as a condition of such
reclassification, reorganization, or change, lawful provision shall be made, and
duly executed documents evidencing the same from the Company or its successor
shall be delivered to the Holder, so that the Holder shall have the right at any
time prior to the expiration of this Warrant to purchase, at a total price equal
to that payable upon the exercise of this Warrant, the kind and amount of shares
of stock and other securities and property receivable in connection with such
reclassification, reorganization, or change by a holder of the same number of
shares of Common Stock as were purchasable by the Holder immediately prior to
such reclassification, reorganization, or change. In any such case appropriate
provisions shall be made with respect to the rights and interest of the Holder
so that the provisions hereof shall thereafter be applicable with respect to any
shares of stock or other securities and property deliverable upon exercise
hereof, and appropriate adjustments shall be made to the purchase price per
share payable hereunder, provided the aggregate purchase price shall remain the
same.

                (c) NOTICE OF ADJUSTMENT. When any adjustment is required to
be made in the number or kind of shares purchasable upon exercise of the
Warrant, or in the Warrant Price, the Company shall promptly notify the
Holder of such event and of the number of shares of Common Stock or other
securities or property thereafter purchasable upon exercise of this Warrant.

            8.  NO FRACTIONAL SALE OR SCRIP. No fractional shares or scrip
representing fractional shares shall be issued upon exercise of this Warrant,
but in lieu of such fractional shares the Company shall make a cash payment
therefor on the basis of the Exercise Price then in effect.

            9.  NO STOCKHOLDER RIGHTS. Prior to exercise of this Warrant, the
Holder shall not be entitled to any rights of a stockholder with respect to the
Shares, including (without limitation) the right to vote such Shares, receive
dividends or other distributions thereon, exercise preemptive rights or be
notified of stockholder meetings, and such Holder shall not be entitled to any
notice or other communication concerning the business affairs of the Company.
However, nothing in this Section 9 shall limit the right of the Holder to be
provided any notices required under this Warrant or the Purchase Agreement.

            10. REGISTRATION. The Company will use reasonable efforts to file an
appropriate registration statement for the shares of common stock to issue from
the warrants on or before August 7, 2001.

            11. TRANSFERS OF WARRANT. Subject to compliance with federal and
state securities laws, this Warrant and all rights hereunder are transferrable
in whole or in part by the Holder to any person or entity upon written notice to
the Company. The transfer shall be recorded on the books of the Company upon the
surrender of this Warrant, properly endorsed, to the Company at its principal
offices, and the payment to the Company of all transfer taxes and other
governmental charges imposed on such transfer. In the event of a partial
transfer, the Company shall issue to the holders one or more appropriate new
warrants.

                                       3

<PAGE>

            12. SUCCESSORS AND ASSIGNS. The terms and provisions of this Warrant
and the Purchase Agreement shall inure to the benefit of, and be binding upon,
the Company and the Holders hereof and their respective successors and assigns.

            13. AMENDMENTS AND WAIVERS. Any term of this Warrant may be amended
and the observance of any term of this Warrant may be waived (either generally
or in a particular instance and either retroactively or prospectively), with the
written consent of the Company and the Holder. Any waiver or amendment effected
in accordance with this Section shall be binding upon each holder of any Shares
purchased under this Warrant at the time outstanding (including securities into
which such Shares have been converted), each future holder of all such Shares,
and the Company.

            14. NOTICES. All notices required under this Warrant and shall be
deemed to have been given or made for all purposes (i) upon personal delivery,
(ii) upon confirmation receipt that the communication was successfully sent to
the applicable number if sent by facsimile, (iii) one day after being sent, when
sent by professional overnight courier service, or (iv) five days after posting
when sent by registered or certified mail. Notices to the Company shall be sent
to the principal office of the Company (or at such other place as the Company
shall notify the Holder hereof in writing). Notices to the Holder shall be sent
to the address of the Holder on the books of the Company (or at such other place
as the Holder shall notify the Company hereof in writing).

            15. ATTORNEY'S FEES. If any action in law or equity is necessary to
enforce or interpret the terms of this Warrant, the prevailing party shall be
entitled to its reasonable attorneys' fees, costs and disbursements in addition
to any other relief to which it may be entitled.

            16. CAPTIONS. The section and subsection headings of this Warrant
are inserted for convenience only and shall not constitute a part of this
Warrant in construing or interpreting any provision hereof.

            17. GOVERNING LAW. This Warrant shall be governed by the laws of the
State of Delaware as applied to agreements among Delaware residents made and to
be performed entirely within the State of Delaware.

            18. DISPUTE RESOLUTION.

            (a) The parties shall use and strictly adhere to the following
dispute resolution processes, except as otherwise expressly provided in this
paragraph, to resolve any and all disputes, controversies or claims, whether
based on contract, tort, statute, fraud, misrepresentation or any other legal or
equitable theory (hereinafter, "Dispute(s)"), arising out of or relating to this
Agreement (and any prior agreement this Agreement supersedes), including without
limitation, its making, termination, non-renewal, its alleged breach and the
subject matter of this Agreement (e.g., products or services furnished hereunder
or those related to those furnished).

            (b) The parties shall first attempt to settle each Dispute through
good faith negotiations. The aggrieved party shall initiate such negotiations by
giving the other party(ies)

                                       4

<PAGE>

written notice of the existence and nature of the Dispute. The other party(ies)
shall in a writing to the aggrieved party acknowledge such notice of Dispute
within ten (10) business days. Such acknowledgement may also set forth any
Dispute that the acknowledging party desires to have resolved in accordance with
this Paragraph.

            (c) Thereafter, if any Dispute is not resolved by the parties
through negotiation within thirty (30) calendar days of the date of the
notice of acknowledgement, either party may terminate informal negotiations
with respect to that Dispute and have the right, by delivery of written
notice thereof (the "Arbitration Notice") to the other party, to submit the
matter to be finally settled by arbitration in accordance with the Commercial
Arbitration Rules then in effect of the American Arbitration Association, as
modified herein (the "AAA Rules"). The place of arbitration shall be Oklahoma
City, Oklahoma if the Arbitration is initiated by Company and San Jose,
California if the Arbitration is initiated by Holder. All matters so
submitted to arbitration shall be settled by three arbitrators. Holder and
Company shall each designate one arbitrator within twenty (20) days of the
delivery of the Arbitration Notice. If either party fails to timely so
designate an arbitrator, the matter shall be resolved by one arbitrator
timely designated. Holder and Company shall cause the designated arbitrators
to mutually agree upon and to designate a third arbitrator, PROVIDED HOWEVER,
that failing such agreement within 45 days of delivery of the Arbitration
Notice, the third arbitrator shall be appointed in accordance with the AAA
Rules. Holder and Company shall each be responsible for the payment of the
fees and expenses of their respectively designated arbitrators and shall bear
equally the fees and expenses of the third arbitrator. Holder and Company
shall cause the arbitrators to decide the matter to be arbitrated pursuant
hereto within sixty (60) days after the appointment of the last arbitrator.
The arbitral tribunal is not empowered to award damages in excess of
compensatory damages or similar damages with respect to any Dispute and each
party hereby irrevocably waives any right to recover punitive, exemplary or
similar damages with respect to any Dispute. The final decision of the
majority of the arbitrators shall be furnished to Holder and Company in
writing and shall constitute a conclusive determination of the matter in
question, binding upon Holder and Company and shall not be contested by any
of them. Such decision may be used in a court of law only for the purpose of
seeking enforcement of the arbitrators' award. Any arbitration proceeding,
decision or award rendered hereunder and the validity, effect and
interpretation of this arbitration agreement shall be governed by the Federal
Arbitration Act, 9 U.S.C. Sections 1-16, and judgment upon any award may be
entered in any court of competent jurisdiction.

            (d) Holder and Company hereby irrevocably consent to the
jurisdiction of the state and federal courts in the States of Oklahoma and
California, and all state and federal courts competent to hear appeals
therefrom, over any actions which may be commenced against any of them under or
in connection with this Agreement. Holder and Company hereby irrevocably waive,
to the fullest extent permitted by applicable law, any objection which any of
them may now or hereafter have to the laying of venue of any such dispute
brought in such court or any defense of inconvenient forum for the maintenance
of such dispute in the Western District of Oklahoma and

                                       5

<PAGE>

Oklahoma County or the Northern District of California and Santa Clara County.

            IN WITNESS WHEREOF, the Company caused this Warrant to be executed
by an officer thereunder duly authorized.

                                   CONDUCTUS, INC.



                                   By: /s/ Charles E. Shalvoy
                                       ----------------------
                                       Charles E. Shalvoy, President and Chief
                                       Executive Officer

                                       6

<PAGE>

                               NOTICE OF EXERCISE



To:   Chief Executive Officer
      Conductus, Inc.
      969 W. Maude Avenue
      Sunnyvale, CA 94086

            The undersigned hereby elects to purchase        shares of Common
Stock of Conductus, Inc., pursuant to the terms of the attached Warrant and
payment of the Exercise Price per share required under such Warrant
accompanies this notice;

x                                             WARRANTHOLDER:



                                             By:
                                                --------------------------------
                                             Name:
                                                  ------------------------------
                                             Title:
                                                   -----------------------------

                                 Address:
                                             -----------------------------------

                                             -----------------------------------

Date:
     --------------


Name in which shares should be registered:


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